This invention relates to a shock absorber, and more particularly to a shock absorber adapted to exhibit increased shock absorbing characteristics.
Various kinds of shock absorbers have been conventionally known in the art. The conventional shock absorbers are generally classified into a shock absorber of the single tube structure type including a single cylinder and a shock absorber of the double tube structure type including an outer cylinder and an inner cylinder arranged so as to be spaced at a predetermined interval from the outer cylinder.
The single cylinder type shock absorber is further classified into a channel orifice type wherein a single cylinder is formed on a peripheral surface thereof with a channel-like orifice and a dashpot type wherein a piston is formed into an outer diameter smaller than an inner diameter of a single cylinder, resulting in a gap therebetween constituting an orifice. The double tube structure type shock absorber is generally constructed so that the inner cylinder is formed with a plurality of holes.
The conventional shock absorbers described above are selected depending on a manufacturing cost and/or applications. In general, the shock absorber of the single tube structure type is reduced in manufacturing cost as compared with that of the double tube structure type, since the former is simplified in construction as compared with the latter. However, the dashpot type shock absorber, of the above-described two shock absorbers of the single tube structure type, theoretically fails to exhibit stable shock absorbing characteristics, to thereby cause a variation in characteristics between products to be disadvantageously increased. The channel orifice type shock absorber minimizes such disadvantages of the dashpot type one. However, the channel orifice type shock absorber requires cutting or molding by a die for formation of the channel orifice. Thus, formation of the groove sufficient to permit the channel orifice type shock absorber to exhibit characteristics suitable for applications requires much time and labor as compared with the shock absorber of the double tube structure type wherein characteristics thereof are adjusted by varying the number of holes formed and/or a size thereof.
Nevertheless, the shock absorber of the double tube structure type has a disadvantage of increasing a manufacturing cost. Another disadvantage of the shock absorber of this type is that a diameter of a piston or a thickness of the inner cylinder is reduced when the outer cylinder is formed into the same outer dimensions as the cylinder of the shock absorber of the single tube structure type, because the piston is arranged in the inner cylinder. It would be considered that such a disadvantage is avoided by increasing the outer dimensions of the outer cylinder. However, this causes the shock absorber to be disadvantageously increased in size. Thus, formation of the shock absorber of the double tube structure type into the same outer dimensions as that of the single tube structure type causes shock absorbing characteristics thereof to be reduced as compared with those of the latter. Unfortunately, this often causes damage to the inner cylinder or the like.